Biological Molecules

Question 1

What do carbohydrates, lipids and proteins all contain ?

Answer 1

Carbon, hydrogen and oxygen

Question 2

What do proteins also contain other than carbon hydrogen and oxygen ?

Answer 2

Nitrogen and sulfur

Question 3

What are the two types of carbohydrates ?

Answer 3

• simple sugars

* complex carbohydrates

Question 4

Describe simple sugars

Answer 4

• soluble in water
• sweet tasting
• Single units of sugar (monosaccharides) or two molecules joined together (disaccharides)
• supply energy from respiration
• examples are glucose, sucrose and lactose

Question 5

Describe a complex carbohydrate

Answer 5

• made of thousands of glucose molecules = they are polymers
• they are storage molecules-starch in plants, glycogen in animals
• insoluble so won’t affect water movement
• compacted so can store large amounts of glucose in a small place

Question 6

What are proteins made up?

Answer 6

Many Amino acids

Question 7

How many amino acid’s are there ?

Answer 7

20, which are joined together in different combinations to make proteins.

Question 8

What does the shape of the protein help ?

Answer 8

The shape helps the protein carry out its job, and the shape depends on its sequence

Question 9

What are the functions of proteins?

Answer 9

• structural molecules
• controlling chemical reactions = enzymes
• Messenger molecules = hormones
• combating disease = antibodies
• transport = haemoglobin

Question 10

What effect does the low-temperature cause on proteins ?

Answer 10

Low temperature has no affect on shape, however it may carry out functions more slowly

Question 11

What affect does high-temperature have on proteins?

Answer 11

High-temperature can change shape irreversibly. This means the protein cannot carry out its function-it has become DENATURED

Question 12

What effect does extreme pH have on proteins ?

Answer 12

They become denatured

Question 13

What are the functions of lipids ?

Answer 13

• Hormones
• insulation
• buoyancy
• Energy store
• blubber
• protection of organs
• main component of cell membrane

Question 14

What are fats and oils ?

Answer 14

Types of lipids

Question 15

What are lipids made up of ?

Answer 15

Glycerol and fatty acid’s

Question 16

What are the two types of fatty acids ?

Answer 16

• saturated fatty acid’s = FATS

* unsaturated fatty acid’s = OILS

Question 17

Describe the Benedict test for glucose

Answer 17

• add 5 cm³ of Benedicks solution to the liquid
• heat using a water bath at 60°
• if you see a colour change from BLUE to BRICK RED glucose is present

Question 18

What test is for glucose ?

Answer 18

Benedicts

Question 19

What test is for starch ?

Answer 19

Iodine

Question 20

Describe the iodine test for starch

Answer 20

• add 5-10 drops of iodine solution to the substance

* it’s starch is present you would serve a colour change from BROWN to BLACK or BLUE

Question 21

What controls chemical reactions ?

Answer 21

Enzymes

Question 22

What are enzymes ?

Answer 22

A group of proteins. Enzymes are biological catalysts

Question 23

What is a catalyst ?

Answer 23

A catalyst is a chemical which increases the rate of reaction without being used up itself in the reaction

Question 24

What is the name for the substance the enzyme acts on ?

Answer 24

Substrate

Question 25

What is the name for the substance produced by the reaction of an enzyme ?

Answer 25

Product

Question 26

What two things can enzymes increase the rate of ?

Answer 26

• catabolic reactions - breaking down large molecules into smaller ones
• anabolic reactions - building large molecules from smaller substrates

Question 27

Describe how enzymes work

Answer 27

• The substrate binds to the active site on the enzyme
• The active site of a particular enzyme has a specific shape which is complimentary to the shape of the substrate
• once the reaction has occurred the products do not fit the active site’s shape anymore so they are released
• after the reaction the enzyme molecule is free to catalyse the next reaction

Question 28

What does binding to the active site enable the reaction to do ?

Answer 28

• Occur with a lower activation energy then without the enzyme. This is how enzymes are able to increase the rate of reaction
• without enzymes reactions would occur to slowly and organisms would die

Question 29

What are the effects of temperature on an enzyme ?

Answer 29

• as temperature increases molecules have more kinetic energy therefore, they move faster. If molecules are moving more quickly, they are more likely to collide with other molecules or with enzymes. This is the reason why reactions involving enzymes happen faster at higher temperatures
• however at extremely high temperatures the shape of the enzyme is irreversibly change, this is because the thermal energy alters the active site, as a result The substrate will no longer be complimentary to the active site, this means the reaction cannot occur. We say that the enzyme is denatured

Question 30

Effects of pH on an enzyme ?

Answer 30

• The shape of an enzyme is also dependent on pH. Each enzyme has its own optimum pH and chemical bonds hold the correct shape at the pH. A significant change in the pH would disrupt the chemical bonds and cause a change in shape, which will mean that the substrate is no longer complimentary to the active site and so cannot bind to the enzyme

Question 31

Effects of surface area on enzymes ?

Answer 31

• enzymes will catalyse reactions more rapidly if the substrate has a larger surface area.
• This is because there is more of the substrate accessible to the enzyme and so more chance of a successful collision between substrate and an active site

Question 32

Effects of concentration of substrates to enzyme

Answer 32

• enzyme reactions will occur more rapidly if the concentration of the substrate and/or enzyme is increased
• this is because there are more successful collisions between the substrate and an active site